The Incredible Science of Coffee Processing Coffee Resource, Top Stories Most of us don’t think about how coffee gets to our mugs. If anything, we know that coffee beans come from coffee trees, and that they get roasted, and then… we drink coffee. While farming and roasting are important (and much more complicated than they sound), there’s an essential step in coffee preparation that everything depends on and that you probably don’t know much about: coffee processing. While coffee processing might not sound like the coolest thing in the world, there are so many things that have to be done right, by so many people, for coffee to turn out. Knowing the effort involved makes every great cup of coffee just a little more miraculous. Let’s take a tour of the coffee processing journey to see just how much effort goes into getting those beans ready for the roasters. You’ll get a good overview of what it takes to prepare beans and have that much more respect for your morning brew. Ripe for Harvest Processing begins once the fruits of the coffee plant, called coffee cherries, are harvested from the coffee plant. The cherries turn from green to red to signify their ripeness. Most coffee-producing countries have one coffee harvest a year, and it’s immense. Harvesting is done differently depending on the location. Sometimes, with cheaper coffee, it’s not only the ripe cherries that are picked – mechanized processes don’t selectively pick the ripest fruit – but some coffee cherries are selectively picked by hand at the optimal time. Once the cherries are off the trees, there are five layers that need to be stripped from the cherries to end up with the bean. Obviously, this isn’t going to happen by hand. There are three general initial processing methods: washed, natural, and semi-washed. Each one works in different areas of the world and produce different flavors for your coffee. Washed Method TIME: 10 days Used in: Countries with high humidity Flavors Results: Fruity notes, gentle acidity The washed method involves – you guessed it – water. To start the process of removing the outer layers, the cherries are soaked in water, and the unripe ones float to the top. The cherries that remain are then fermented with microbes in water for a day to a day and a half, enough to soak into and loosen the first three layers. The beans have to be monitored so that no funky flavors form because of the microbes. When the fermentation is just right, the beans are drained and either re-washed or put through a machine to remove the three layers. Once that’s done, beans still need to dry, and the final two layers, called the parchment and the silver skin, need to be removed. Some beans are dried in the sun, but due to weather and local humidity conditions in certain countries, it’s not arid enough to finish drying the beans before mildew forms. In more humid countries, beans are dried by machine, and then the parchment and silver skin are usually removed before the beans are sold. Our Washed Coffees: Natural Method TIME: 4 weeks Used in: Countries with lower humidity Flavors Results: Heavier, complex flavors The natural method is almost the exact opposite of the washed method. Ripe and unripe cherries are sorted by hand in a sieve or other container, and then the beans are put out into the sun to dry. Sounds simple, right? Maybe not, when you consider that the beans need to dry for up to four weeks before the moisture level is right – and they need to be constantly turned by hand to keep them drying evenly. Time drying time also changes depending on whether the beans are on the ground or on elevated drying racks. Our Natural Coffees: Semi-Washed Method TIME: 25 days Used in: Countries with lower humidity Flavors Results: Reduced acidity, increased body In the semi-washed method, the outer layers of the cherries are removed by machine, and then the beans are washed off before being dried in the sun or by machine. This combined method has the benefit of cleaning the beans with water, without fermentation, and that the beans will dry faster, since they don’t have as many layers when they’re put out in the sun. Our Semi-Washed Coffees: Final Steps For all these methods, once the beans are dry enough, they’re sent to complete the final processing steps. These step has its own complications, because when the beans arrive for milling, there’s more than beans there: there may be some parchment or silver skin remaining on the beans, and there may also be rocks, dirt, and other debris gathered after the drying process. Hulling Hulling removes the outer layer from the beans, whether it’s the last bits from washed beans or all the outer layers left during the natural method. Moisture content makes a lot of difference here. If beans are too dry, they might crumble during the mechanical hulling process. Just one more step where everything needs to be just right. When hulling is complete, all that’s left of the original cherries are the green coffee beans, which won’t turn brown until they’re roasted. Sorting The sorting process makes sure only the best beans make it to the final stage. All foreign matter is removed in this step, usually by blowing the beans into the air. The beans are sorted by weight – the heavier, the better – and also by color. The color-sorting process is often done by hand, but there are even computer-controlled pneumatic machines that watch pouring streams of beans and shoot defective ones out of the stream with compressed air. Decaffeination and Other Steps We’re almost to the end! While there are a few optional steps that might happen during milling, including polishing, aging, and grading, the most interesting one is decaffeination. How in the world is the most important chemical from coffee removed from coffee beans? Usually, with more chemicals. The green coffee beans are moistened and either soaked in oil or alcohol or put through super-compressed carbon dioxide at 4,000 psi. However, our decaffeinated coffee, the Guatemala, is processed with water, a process that doesn’t risk affecting the vulnerable flavor of the beans. Storage and Transportation Coffee beans are stored and transported in jute bags, where they can be kept for up to several years. The care with which they were first picked and processed needs to be taken with the beans until they’re roasted, since mold can form and everything that happens to the bean, from where it’s stored to what air it comes in contact with, will affect its flavor. Next Step: Roasting Coffee is a huge economic driver for many countries in part because it employs so many people. Between the washed, natural, and semi-washed processing, between turning and color-sorting the green coffee beans, so many people have literally had a hand in taking your coffee from the tree to the roastery. Flavor isn’t the only reason why the source of coffee is so important: you’re supporting many people’s livelihoods by investing in great coffee. Next, we’ll look at the final step of coffee preparation and flavoring: roasting. Until then, let’s raise our mugs and toast to the many people who’ve worked hard to process our coffee beans.